Merging of Universes
by TheK1ng
Summary: The Crisis on Earth X ended very differently. Overgirl went full supernova on everyone. Barry had to do something so he did what he does best. Messing with Time.


**Chapter 1**

As Barry Allen looked around him, he saw the world around him move in slow-motion. Now that wasn't really a novelty experience for him, since the world, to him at least, always seemed to move a bit slowly. A side effect of being the fastest man alive.

But since he could willingly decide just how fast the world around him moved (well more like just how fast he perceived the world around him, since slowing down time wasn't really in his skillset), it wasn't the worst side effect to be had, for sure, and most of the times it was a very useful tool to give him time to think things through in hectic or stressful situations, it also allowed Barry to go off on random tangents in situations he should be focusing on the task at hand, for example right now (Barry knew that if Oliver knew just how easily he was distracted in the face of a possibly world ending situation, he would probably shoot Barry again and then berate him for getting distracted to easily. Oliver probably had a point, Barry admitted silently to himself).

So, focus on the problem at hand, Barry chastised himself. Evil Doppelgangers trying to kill Kara aka Supergirl aka the best person/alien he knew by stealing her heart (literally, how crazy was that?) and destroy or at least subjugate his home-universe. Evil Nazi Doppelgangers at that. As if interrupting his wedding to the woman of his dreams just before they finally could be married wasn't enough. Maybe he should have just stayed in bed today.

Anyways back to the invasion happening right know. Barry had just beaten the Reverse Flash once again. (Seriously when would Thawne ever learn that he just couldn't win. It was getting boring at this point. After the first Reverse Flash appearance, that mess with Zoom and the supposed God of Speed, Savitar his quota for evil speedsters had been filled for more than one lifetime. So even though he was a recurring enemy, the Reverse Flash at this point was just an old, worn out hat.)

He saw Oliver winning his fight against his evil doppelganger, gaining the edge slowly but surely and if he interpreted the shouts of joy coming through the comms right, the others of this weird Superhero-team-up were having just as much success in their respective fights. Hopefully no one else would die today. One funeral was already way too much.

Just as that thought coursed through his mind he caught sight of the two fighting Karas. A foreboding feeling coursed through him as the next few seconds played out before him.

Kara (Supergirl) punched Kara (Overgirl) hard in the face, knocking her into the ground while at the same time Kara (Supergirl) got hit by a beam of heat vision from Kara (Overgirl), simultaneously knocking out both Karas. While normally having knocked out the enemy's best soldier would count as a win for their team, there was a problem. A big problem. A "fuck my world is going down in a supernova" problem. Because Overgirl was still unstable from the overexposure of solar radiation and about to go nuclear on them.

As the closest person to both Karas he first noticed the glowing cracks of light bursting through the skin of Overgirl. The cracks quickly expanded and rapidly encased Overgirl as a whole. She started to glow brighter and brighter. Barry could feel the heat of a dying star flaring around him. Since Kara was still out cold next to him no one would be able to get Overgirl faraway enough from earth to save them. They were all dead and no one would be able to do anything to prevent it. Fuck

Just as the realization of their inevitable demise fully hit Barry, the light started to expand with the intensity of a dying star, mixing rays of yellow and orange into the glowing mass of destruction that would be the end for all of them.

Barry reacted more on instinct than anything else at this point as he grabbed Kara (Supergirl) and started running. He could feel the familiar feeling of the speed force encase him as white lightning crackled around his form. So, he took off, feeling the wind around him, the heat burning threateningly behind him and the familiar weight of Kara securely in his arms. Without knowing where he was going to run, just knowing that he needed to go faster Barry trusted his instincts and emerged himself deeper into the Speed Force. Going even faster, the lightning around him turning a mixture of dark blue and gold he tore straight through the barriers that kept the timeline straight and the different universes apart. They were surrounded by the familiar blue nexus that accompanied him through all his mishaps with time and universe travels, until suddenly there were no more lights or sounds or anything really. Just him and Kara floating around in the nothingness. Through the nothingness he felt a by now familiar pull of the speed force. Without offering any resistance suddenly him and Kara were in the familiar space of his childhood bedroom. The last thing he saw, before the exhaustion caught up with him and he passed out was the smiling face of his mother worn once again by the Speed Force.

When he woke up Barry felt warm and safe. Arms encircling him in a tight grip as he lay on his back and a head cuddled against his chest. The moment he opened his eyes he saw a mop of soft blond locks sprawled all over him. The events of the past hours caught up with him as a sob wrecked through him. Everyone he knew and loved was dead. His entire Earth gone. Silent tears rolled down his cheeks as he tightened his grip around the still sleeping Kara. The last remnant of his friends and family.

Before he could lament the fate of his universe more a strange feeling of serenity settled inside of him as his mother entered the room. Strangely enough she was smiling. Before he could open his mouth to unload the thousands of questions coursing through his mind at rapid speeds, his mother started speaking.

"We are unbelievably proud of you, Barry Allen." She spoke with a motherly smile on her face. "You have finally released a part of the near endless speed potential we knew you had inside of."

"What does it matter?" Barry mumbled bitterly. "What does my potential matter?" He paused. "What does my speed matter, when in the end everything is gone anyways? My whole Earth is gone! Everybody I care about is gone! My life is gone! So, please enlighten me how would anything still even matter?" Barry agonized desperately. No answer. Barry really hadn't expected an answer anyways. Taking a deep breath, he looked up at his mother. She still wore a smile on her face, but it had been slightly dimmed. Suddenly his vision blurred, feeling suddenly very much drained.

"Worry not, Bartholomew." She told him. "Everything will work itself out. You will have the opportunity to save all of your friends. Expect some changes in your world." And with that cryptic message she stepped closer to him, touched his cheek softly with one hand and placed a soft kiss on his forehead, as he felt the world around him go darker he caught a last quiet whisper in his mother's voice. "Ohh, and by the way tell Kara "Hello" from us."

And then there was darkness.

Barry woke up to the sound of Lady Gaga's "Poker face" blaring through the Lab as he rouse up violently from his sleep.

He vaguely heard a drawled "Oh my god" from Cisco, when suddenly someone (Caitlin if he heard right) blended him by shining a flashlight into his eyes.

Woah. Deja Vue.

He tried to get up rather groggily, only for Caitlin to gently but firmly push him back into the mattress. Overwhelmed with confusion he barely managed to get out an "Where am I? What's going on?" before Caitlin was back to poking him all over while Cisco tried to explain the situation to him.

Barry barely heard a word spoken by Cisco, too focused on trying to make sense of the world around him, endless possibilities coursing through his mind at high speeds until finally he heard the one sentence that confirmed his growing suspicion "I need you to urinate in this cup for me!"

He had time travelled. Once again. To the beginning of his superhero journey. Huh. So that's what the Speed Force meant.

In a trance he shot up, barely registering the fact that he was half-naked.

Mistaking his silence for confusion they explained to him that he was hit by lightning and had been in a coma.

Slightly amused and a little bit perplexed still, the only thing Barry could say (once again) was "Lightning gave me abs?"

He had to stifle a smile seeing that Caitlin started to explain how his muscles should have been atrophied due to not being used and how they were instead in a chronic (and unexplained) state of cellular regeneration. While Caitlin talked Cisco gave him a Star-Labs sweatshirt to cover himself up that he quickly put on. Just to check if anything had changed Barry asked "How long was I out for?"

And just as he remembered the voice of Harrison Wells answered "9 months." After Barry had turned to look at him Wells continued "Welcome back Mr. Allen. We have a lot to discuss."

In a daze, Barry followed after Dr. Wells, not quite sure how to react and certain of the fact that he couldn't just randomly attack someone without any kind of evidence. He silently wondered how the defense of "He is an evil time-traveling speedster from the future that killed my mother and is here to kill me and all my friends. How I know that, you ask? Simply I am a time-traveler myself" would hold up in court. Barry doubted that it would work. Also, he shouldn't reveal his future knowledge to one of his greatest enemies, Barry thought as an afterthought.

So, he pretended to be awestruck by Dr. Wells, explaining how long he had dreamed about meeting the man and how much he admired his work.

After Wells had explained about the "failed" particle accelerator, the anomaly and how Barry had ended up in Star Labs, Barry managed to excuse himself the way he had done the first time around and left the building. He kept the Sweatshirt (of course).

As he needed to gather his thoughts (and to check if he still had his powers) Barry went for a run. As he started he could feel the Speed force coursing through him and he blasted off. So, yep. Powers still there and he felt himself go way faster than when he first started. Almost to the levels of speed he managed before he traveled back in time. Those levels he would probably get to with more training.

Having cleared his head he stopped for a moment to think about what he was going to do next. His first priority would be to talk to Joe and Iris. Damn Iris. The woman he would have had been about to marry. The woman he had been in love with forever. The woman who right now had a living boyfriend, who would move on to become her fiancé. The boyfriend Barry could save now. After all he was stronger, smarter and better prepared this time around. But saving Eddie would mean that he would live on to marry Iris. Meaning no Iris West-Allen in the future. Of course, Barry thought darkly, he could just let it all play out the same way as before. But he wouldn't. He couldn't. That wasn't him. Iris deserved happiness and if that happiness came from someone else then Barry would learn to live with that. He had to. Afterall he was a Superhero. He was the Flash. (Or would be soon enough). He would do it. He would save Eddie and if that meant that he would be unhappy then so be it. Fuck. Time-travel was already annoying him.

Having enough of his depressing thoughts Barry decided to just go and look for Joe and/or Iris.

Barry found Iris where he found her the first time around, in Jitters. She was waiting a table as he stepped inside. She looked even more beautiful than he remembered. It felt like years since he had last seen her, while in reality it had only been about two days.

Before he could ponder more on that Iris looked up, as if sensing his gaze on her. She nearly dropped the tablet she was holding as she rushed to get to him, a wide, teary smile gracing her face. Barry returned the sentiment and he could swear he felt his heart stop beating and the world stop turning as she looked at him. He managed to resist the urge to kiss her, but it was harder for him than he would like to admit. Well this was going to be a bitch.

She engulfed him in a tight embrace, holding on to him as if he would disappear any second.

As she finally let go of him she looked him in the eyes and he could see the "investigative-reporter-look" (that he knew so well and loved very much) on Irises face, right before she started her onslaught of questions "When did you wake up? Why didn't Star Labs call? Should you be up? How are you? I can't believe that you are up. Am I dreaming?"

And she would have continued if Barry hadn't interrupted her by pulling her in for another hug. This time he was the one holding on for dear life, reliving all the wonderful memories he had made with his Iris in the future. The future that would be impossible to return too. Barry would change things, he knew that. He had to. After all, if he let it play out as it had before so many people would die. People he had the responsibility to save.

So, Barry let go of Iris with a deep shuddering breath after a long moment of just holding her. For him this gesture meant so much more than just releasing her from his embrace, with him releasing her he also (for now) let go of the future with Iris as his wife, knowing that if they were meant to be that they would find a way.

A single tear ran down his cheek as he told Iris "I am fine, you don't need to worry too much, please." And he forced himself to smile at her even though he felt like he was breaking to pieces inside.

"I watched you die, Barry!" Iris told him with a worried frown on her face. "Your heart kept giving out." She continued in a soft whisper "I can't lose you, Barr. You are one of the most important persons in my life."

Barry felt his heart break a little bit more, for both him and her. "Don't worry Iris, I am okay and I promise you that I will do everything in my power to stay in your life for as long as you want and need me to." He said while pulling her in for yet another embrace. "I will want you around for as long as I life, Barr" Iris whispered into his chest. Those words gave him hope. Afterall this Iris was at least still his best friend, even if that was all it would ever be, he still would have her in his life.

After that their catching up took a noticeable lighter direction as they joked around, while Iris caught him up on everything that he missed while he was passed out.

An hour later Barry and Iris walked arm in arm out of Jitters, on their way to the Central City Police precinct, after Barry had mentioned that he hadn't told Joe yet that he was awake. Iris didn't seem to want to let go of Barry, afraid that he would disappear any moment. And he was fine with that.

At the precinct Barry and Iris easily spotted Joe even though his back was turned to them and walked over to him. Iris tapped her father on his shoulder and Barry would swear that Joe had just moved in superspeed because before even he could react Joe had him in a tight embrace. In contrast to his reunion with Iris, this reunion was a lot more lighthearted, after all for Joe his son had just waken up from a coma and Barry still had the same relationship with Joe here as he had in the future.

Many other officers welcomed him back with their usual comments about him being and looking young (So much originality coming from everyone, Barry thought sarcastically).

Detective Chyre still had died the night of the practical exhilarator, that was a bummer, but it also helped Barry figure out that everything was still the same. Just as he thought that, two police officers walked in with the loosely secured perp. Just like he remembered the perp made a grab for one of the two officers' guns, which Barry prevented by speeding at him, slapping it out of the perp's hand and then speeding back to his previous place, with the only sign of movement being a slight breeze of air running through the precinct. Crisis averted without anyone suspecting anything, Barry returned to his conversation with Joe and Iris.

Or he would have if Joe hadn't been called away by Eddie to deal with a bank robbery. Barry of course noticed the looks exchanged by Iris and Eddie, but chose not to comment.

Suddenly Barry was hit by a thought, this bank robbery was probably the one carried out by his first meta human enemy, Clyde Mardon. The Police wouldn't be able to stop Mardon without his help, but he knew that he couldn't just simply use his speed like it always had been a part of him, because that would be a dead giveaway which Thawne would probably easily pick up on. He had to do what he did last time. Go to the people who had given him his speed and ask for their help in understanding what was happening to him, even if that meant pretending not to know that it was Thawne who had killed his mother. Although with the excitement settling in about getting to befriend his two future best friends and partners in crime (well partners in superheroing) all over again that didn't seem like such a hard thing to do. And with that thought he was off on his way to Star Labs.

The next day Barry and the Star Labs team were at an abandoned airfield, with an entire setup to monitor his vitals and the ridiculous red bodysuit Cisco had forced him to wear.

As Caitlin fine tuned the last of the monitoring tech, Barry couldn't help but look at her worriedly. This was the guarded, unsmiling Caitlin Snow that felt like she had lost everything (which she had every right to, after all her life after the Explosion had basically imploded on itself). Barry was determined to help her through it all and make her feel needed in a world where she was kinda floating around aimlessly. He also wondered if Killer Frost was still in her or if she would exist ever again.

Before he could ponder more on that Caitlin noticed him looking at her and snapped at him sharply "What?"

"Nothing." Barry answered awkwardly "I just noticed that you don't smile too much." He added as an afterthought

"Well my once promising career in Bioengineering literally blew up in my face and is heading nowhere. The same explosion that crippled my boss also killed my fiancée, so this expression kinda feels like the way to go, right now."

Barry looked at her with sympathy written all over his face and told her "I know that we aren't friends nor do we really know each other at all, but if you need anything, even if it is just a shoulder to cry on or somebody to use as a punching bag you can call on me. Just give me a call or text me or something and I'll be there in a flash."

Caitlin looked at him skeptically, until she realized that he was serious, then her expression changed into a small, but sincere smile and she told him "I'll think about it." With those words she finished calibrating his pulse meter and walked off, rejoining Dr. Wells at his monitoring desk.

Barry prepared himself to start running, while Cisco got in position behind him with a radar gun in hand. As he took off Cisco got blown away from the aftershock, while Barry just did what amounted to him as something like a light jog, casually passing 600mph.

Instead of crashing into the water barrels like the first time around Barry just ran a Lap, before coming to a halt back at his starting point. Caitlin looked thoroughly shocked, while Cisco looked like he could barely contain his excitement at something that was basically a dream come true for him, real life superpowers.

Barry just stood awkwardly, waiting for someone to say something. "That was freaking awesome" Cisco exclaimed, while Caitlin still seemed frozen in shock. "Yeah it kind of is, isn't it?" Barry said while scratching his neck awkwardly.

Once Caitlin processed what she had just seen, her scientific curiosity kicked in and she started figuratively poking Barry all over, trying to figure out how it was possible for his body too handle the strain of going at such high speeds, while simultaneously asking him how he did it ("By running, duh."), how he felt ("Really great, also very hungry.") and if she could run some tests on him ("Of course, but only after he had eaten").

Dr. Wells just sat still on the sidelines, watching everything play out in front of him, while silently thinking that his long-time investments and planning would finally bear fruits. He was really close to returning to his time now. Still this level of speed this early on did surprise him.

"Anyone up for some Big Belly Burger?" Barry asked around, after he had finally appeased Caitlin with promises that he would let her run all the test she wanted to run on him tomorrow.

Since Cisco didn't have anything better to do, he immediately agreed, while Caitlin took some more convincing from both Cisco and Barry to agree to come. Ultimately it was Barry who managed to convince her with the argument that he would like to get to know the people better who had saved his life.

Dr. Wells just politely declined, stating that he had to take care of some urgent matters that had come up.

Later in the evening once Barry had returned home (to Joe's place) from his outing with his future best friends, he discovered that Mardon was still at large, wreaking havoc with his newfound Meta-Powers. Knowing that he would have to do something about him, Barry decided that he would confront the Star Labs crew tomorrow, to once again get their assistance in saving the city. With those thoughts Barry said goodnight to Joe and went to bed, easily falling into an uneasy sleep, his mind overwhelmed from all the happenings of the past (or future) 48 hours.

The next morning Barry stormed into Star Labs intend on confronting Dr. Wells about the meta humans resulting from the particle accelerator explosion and determined to get their help in dealing with them. The entire confrontation went about the same way it did the first time around, with Barry, to his relief, gaining, after some convincing, the support of Caitlin and Dr. Wells (Cisco had been on board the second he heard about someone playing at being a Superhero "Yeah sure, Superpowered Heroes and Villains duking it out are like all of my fantasies come true.", He had said.)

He even got his very first suit once again, so that was cool.

Once he had (with some future knowledge as help) located Mardon, Barry went to stop him. The events played out nearly the same as the first time, with Barry saving Joe and Eddie, Mardon creating a gigantic Tornado and Barry unraveling it and saving the day. This time around he didn't need any speeches from Dr. Wells as motivation, since to be honest Mardon was a piece of cake for Barry now. He had dealt (or would be dealing, honestly time-travel of this magnitude was just one gigantic headache) with so many stronger enemies that Mardon was like a common thug. He had still revealed himself to Joe after Joe had shot Mardon to "save" Barry and Joe still tried to get Barry to agree not to tell Iris about his speed, but Barry just made some noncommittal noises, since he wasn't to keen on repeating the mistake that had nearly cost him his friendship with Iris. He would wait with revealing himself to Iris to after she started blogging about him, that was after all what got her her first job as a journalist.

Anyways after leaving the suit at STAR-Labs, Barry went back to his dark, lonely apartment. Even before it had never felt like home (one of the reasons he had moved back in with Joe in his previous timeline), but after living with Iris in their warm, homely apartment for the better part of 2 years it felt even worse. Another part of the future that he might never get back.

To distract himself from his darker thoughts Barry switched on the TV, so he had some background noise to fill the void. Even so his thoughts turned progressively more pessimistic. What would he do this time around? Change things? What if he fucked up this timeline? Did him going back in time change everything? Did he lose his shot at a life with Iris? What if somehow a bunch of new, stronger enemies would appear?

Trying to get himself out of his downward spiral, Barry jokingly told himself that he started to sound like Oliver with all that pessimism. Thinking of Oliver Barry realized that he hadn't yet visited the Starling City Vigilante, like he did last time around. That would clear his head at least and it would be nice confirming that Oliver was still alive and not burned to death in a Nazi Kryptonian induced Supernova.

Shrugging, while thinking to himself that now was as good a time as any Barry stood up when the TV caught his attention. In National City a Plane Crash seemed to have been averted by a mysterious flying someone. IF Barry remembered correctly that was how Kara's superhero journey had started. (They had exchanged some stories during downtime.) But that couldn't be possible since Kara didn't live in the same universe as he did. At least she didn't use to. Remembering what the Speedforce aspect of his mother told him, Barry began to hope. Maybe it was future Kara that had somehow traveled through time with him. It was possible after all he had been carrying her when he time-traveled.

Realizing that overthinking the situation wouldn't be of any help right now, Barry choose what would be the simplest way to confirm his thought process. Travelling to National City.

Halfway on his way to National City he realized that he could be grasping at straws and that it was highly possible that he would be disappointed. Not wanting to quit though, Barry continued onwards and in record time arrived in National City.

National City at night was just as beautiful as Central City was. Making his way through the city Barry arrived at his destination, Karas apartment. Just as he was about to knock, the door opened and an upset Alex Danvers stormed out of the door and passed him, not even noticing him (not that she would recognize him.)

To be polite (and on the off chance that he was wrong and that Kara would have no clue about who he was) Barry knocked at the door, patiently waiting for Kara to open it. The door opened slowly with a visibly confused Kara slowly revealing herself standing in the doorway. "Barry?" She asked her confusion bleeding more into her features. "What is going on? How are we here? I thought you weren't supposed to time travel anymore. What happened to change your mind? All I remember is getting knocked out."

Before she could continue talking, a relieved Barry cut her off by pulling her into an embrace. "You remember." He exclaimed excitedly, before he turned more somber "The Kara of Earth-X went nuclear, I couldn't do anything to stop it. Everyone died, I managed to grab you before I ran off. I ran faster than I ever have before, while doing so I must have shattered the dimensional barrier between our dimensions, because we know kind of live on the same Planet. I hope that is the only price we have to pay for me time traveling again, but anything is better than the total annihilation of the universe."

Kara looked at him sympathetically nodding slightly into his chest, showing that she agreed with him. After about a minute of Barry quietly sobbing while holding on to her, Kara guided him inside. Letting go of her Barry sagged exhaustedly into the couch, the events of the past few days catching up with him. Kara positioned herself next to Barry, pulling his head into her lap, stroking his hair, offering silent comfort.

"Of everyone I have ever met, you are probably the only person to understand how it feels to watch your entire planet die before your very own eyes." Barry whispered.

They stayed silent for a bit, both contemplating their situation. Finally, Kara spoke up "You wouldn't believe how confused I was waking up, going back to my job as Cat Grants assistant, Winn talking to me about some date with a guy I had matched with online, don't judge, Alex's plane crashing and me saving it and now her getting mad at me because I showed the world my powers. Luckily, we talked about your ability to time travel or I would have been way more confused than I was. But just now I realized something. We, the two of us, were given something that the entirety of Krypton never got, a second chance at saving our home. We can do better than before, Barry, we can prepare for the invasion and prevent the destruction of our world from ever happening, this is an incredible gift for the two of us." Kara looked Barry in the eyes as she spoke with a radiant smile on her beautiful face.

Looking at her as she looked at him with so much hope and confidence in them Barry could feel a smile grow on his face too. He was given a second chance and the best part was that he wasn't alone. He had help from one of the best persons he knew. They would save their world and all of their friends. "Thank you, Kara." He whispered, returning her smile just as brightly.

The both of them knew that they would have a lot more stuff to figure out, if they truly wanted to make a difference but for the moment they allowed themselves to be distracted to brighten up their moods. To do that they of course ordered pizza and watched musicals until they fell asleep together on Karas couch, holding onto each other for emotional comfort and to chase away any and all nightmares.


End file.
